The present invention relates generally to transmissions for use in motor vehicles and, more particularly, to a twin-clutch automated transmission applicable for use in rear-wheel drive vehicles.
Automobile manufacturers continuously strive to improve fuel efficiency. This effort to improve fuel efficiency, however, is typically offset by the need to provide enhanced comfort and convenience to the vehicle operator. For example, it is well known that manual transmissions are more fuel efficient than automatic transmissions, yet a majority of all passenger vehicles are equipped with automatic transmissions due to the increased convenience they provide.
More recently, xe2x80x9cautomatedxe2x80x9d variants of conventional manual transmissions have been developed which shift automatically without any input from the vehicle operator. Such automated transmissions typically include a plurality of power-operated actuators that are controlled by a transmission controller to shift traditional synchronized dog clutches. However, such automated transmissions have the disadvantage that there is a power interruption in the drive connection between the input shaft and the output shaft during sequential gear shifting. Power interrupted shifting results in a harsh shift feel which is generally considered to be unacceptable when compared to smooth shift feel associated with most automatic transmissions. To overcome this problem, automated twin-clutch transmissions have been developed which can be powershifted to permit gearshifts to be made under load. Examples of such automated manual transmissions are shown in U.S. Pat. Nos. 5,966,989 and 5,890,392. While such powershift twin-clutch transmissions overcome several drawbacks associated with conventional single-clutch automated transmissions, a need exists to develop simpler and more robust transmissions which advance the automotive transmission technology.
Accordingly, it is an object of the present invention to provide a dual-countershaft twin-clutch transmission and a control system for permitting automatic shifting of transmission.
As a related object, the twin-clutch automated transmission of the present invention has a compact geartrain and is applicable for use in rear-wheel drive vehicles.
These and other objects of the present invention are met by providing an automated dual-countershaft twin-clutch multi-speed transmission adapted to transfer power from the engine to a driveline of a motor vehicle. The transmission includes a first master clutch operable to establish a releasable drive connection between the input shaft and a first countershaft, a first motor/generator connected to the first countershaft, a second master clutch operable to establish a releasable drive connection between the input shaft and a second countershaft, a second motor/generator connected to the second countershaft, an output shaft adapted to transfer power to the driveline, and a geartrain for selectively establishing a plurality of forward and reverse speed ratio drive connections between the countershafts and the output shaft. The transmission further includes power-operated dog clutches for selectively engaging constant-mesh gearsets associated with the geartrain, and a transmission controller for controlling coordinated actuation of the first and second master clutches, the first and second motor/generator, and the power-operated dog clutches to permit non-power interrupted (xe2x80x9cpowershiftxe2x80x9d) sequential gear changes automatically without input from the vehicle operator. When shifting under power between gear ratios, one master clutch is released and the corresponding motor/generator is actuated to accelerate/decelerate the released countershaft into speed synchronization with the output shaft. Following completion of speed synchronization, the dog clutch for the selected gearset on the released countershaft is actuated and thereafter the released master clutch is re-engaged.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the scope of this invention will become apparent to those skilled in the art.